Erase block command is one of Mass Erase commands. And if you look at 29.4.5 Allowed Simultaneous P-Flash and EEPROM Operations, you may notice that P-flash simultaneous Read from P-flash and Mass Erase EEPROM is not allowed. Effect of this is that P-flash is not readable while Mass Erase command is applied to EEPROM block. CPU is unable to read code (and interrupt vectors) from P-flash and runs away. You need to either use sector erase command and iterate with it over entire EEPROM array, or move parts of your code from P-flash to RAM.

Erase block command is one of Mass Erase commands. And if you look at 29.4.5 Allowed Simultaneous P-Flash and EEPROM Operations, you may notice that P-flash simultaneous Read from P-flash and Mass Erase EEPROM is not allowed. Effect of this is that P-flash is not readable while Mass Erase command is applied to EEPROM block. CPU is unable to read code (and interrupt vectors) from P-flash and runs away. You need to either use sector erase command and iterate with it over entire EEPROM array, or move parts of your code from P-flash to RAM.